Method of forming contact structure of gate structure

ABSTRACT

A method of forming a contact structure of a gate structure is provided. In the method, an oxidation layer and a first sidewall layer disposed between a first metal gate and a second metal gate are etched to expose an underlying silicon substrate. A silicide portion defined by a contact profile is deposited in the exposed portion of the silicon substrate. A second sidewall layer substantially covers the first sidewall layer and at least partially covering the silicide portion is formed after depositing the silicide portion. A metal glue layer is deposited around the first metal gate and the second metal gate defining a trench above the silicide portion. A metal plug is deposited within the trench.

FIELD

This disclosure relates to semiconductor technology, and moreparticularly, a method of forming a contact structure of a gatestructure.

BACKGROUND

In a contact formation process of a gate structure of a MOSFET, acontact structure is patterned by lithography and etching, and asilicide portion is formed via a pattern of the contact structure.However, the small size of the silicide portion may decrease thestability and the capability of the contact structure after formation ofthe contact structure is complete.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of a contact structure of agate structure.

FIG. 2 illustrates a cross-sectional view of a contact structure of agate structure after forming a silicide layer.

FIGS. 3-8 illustrate various cross-sectional views of a contactstructure of a gate structure during formation of the contact structureaccording to a first embodiment.

FIGS. 9-10 illustrate various cross-sectional views of a contactstructure of a gate structure during formation of the contact structureaccording to the second embodiment.

FIG. 11 illustrates a flowchart of a method of forming a contactstructure of a contact structure according to the first embodiment.

FIG. 12 illustrates a flowchart of a method of forming a contactstructure of a contact structure according to the second embodiment.

DETAILED DESCRIPTION

FIG. 1 illustrates a cross-sectional view of a contact structure 100 ofa gate structure. The contact structure 100 includes a hard mask layer110, a metal gate layer 120, a substrate layer 130, an epitaxial layer140, an insulator layer 150 for the hard mask layer 110, a gap-filllayer 160, a first gate 151, and a second gate 155.

The first gate 151 includes part of the hard mask layer 110, part of themetal gate layer 120, a first left-side spacer 152, and a firstright-side spacer 154. The second gate 155 includes part of the hardmask layer 110, part of the metal gate layer 120, a second left-sidespacer 156, and a second right-side spacer 158.

Under a self-align contact process, if the hard mask layer 110 is notthick enough, after a gap-filling process for depositing the gap-filllayer 160, heights of the first gate 151 and the second gate 155 may notbe high enough; a process for pushing the metal gate layer 120 downwardsmay not succeed; and the gap-filling process may not succeed. Moreover,using the hard mask layer 110 may raise complexity of forming thecontact structure 100, and difficulty of precisely aligning a contactstructure for the epitaxial layer 140, which will be formed into asource or a drain.

FIG. 2 illustrates a cross-sectional view of a contact structure 200 ofa gate structure after forming a silicide layer. The contact structure200 includes a contact layer 210, a first gate 222, a second gate 224,an oxidation layer 230, a silicide layer 240, and an insulator layer250. The insulator layer 250 is utilized for coating most of the firstgate 222 and the second gate 224. The insulator layer 250 is alsoutilized for isolating the first gate 222 and the second gate 224 fromthe contact layer 210 to reduce hole and electron scattering.

Before formation of the contact structure 200, a photolithographyprocess and an etching process are performed. A trench holding thecontact layer 210 is thus formed between the first gate 222 and thesecond gate 224. The trench may have a high aspect ratio. Whiledepositing the contact layer 210 within the trench, the high aspectratio of the trench limits a contact area of a bottom of the contactlayer 210. The limited contact area of the bottom of the contact layer210 also limits an area of the sicilide layer 240.

The small area of the silicide layer 240 also results in largeresistance of the silicide layer 240, and operation of the contactstructure 200 will be difficult to manipulate due to the largeresistance of the silicide layer 240.

If a width of the insulator layer 250 (such as a width 252 or a width254 shown in FIG. 2) is not large enough, the hole and electronscattering between the contact layer 210 and the first gate 222 or thesecond gate 224 may not be effectively alleviated. However, a largewidth of the insulator layer 250 also results in a high aspect ratio ofthe trench holding the contact layer 210 and a small area of thesilicide layer 240, and results in an increased size the contactstructure 200.

If the area of the silicide layer 240 is limited, i.e. a contact size ofthe contact structure 200, flexibility of critical dimension uniformity(CDU) of the contact structure 200 may also be restricted.

In one example, the silicide layer 240 may consist essentially of NiSi,and a temperature of forming the silicide layer 240 may be about 400-500centigrade degrees. However, since formation of the contact structure200 may experience a high-K metal gate last (HK-last) process, and sincea temperature of using the high-K metal gate last process may be about800-1000 centigrade degrees, the silicide layer 240 may be damaged bythe high temperature of the high-K metal gate last process.

FIGS. 3-8 illustrate various cross-sectional views of a contactstructure 300 of a gate structure during formation of the contactstructure 300 according to a first embodiment.

In FIG. 3, the contact structure 300 includes a silicon substrate 320, afirst metal gate 330, a second metal gate 340, a first sidewall layer350, and an oxidation layer 360.

A high-K metal gate last process has been completed to form the firstmetal gate 330 and the second metal gate 340. The first metal gate 330includes a first metal body 332 and a first spacer 334 for at leastpartially coating the first metal body 332. The second gate 340 includesa second metal body 342 and a second spacer 344 for at least partiallycoating the second metal body 342.

The first sidewall layer 350 is interposed between the first gate 330and the second gate 340. A first lateral side (e.g. the right side) ofthe first metal gate 330 is oppose to a second lateral side (e.g. theleft side) of the second metal gate 340.

In a first example, the first sidewall layer 350 is formed using anitride-based film because of having high selectivity for withstandingetchants used in at least one following etching process.

In a second example, the first sidewall layer 350 is formed using amaterial selected from the group consisting of SiN_(x),SiO_((1-x))N_(x), SiC_((1-x))N_(x), SiO_((1-x-y))C_(x)N_(y),Ti_((1-x))N_(x), and Al_((1-x))N_(x). The material also has a highselectivity for withstanding etchants used in at least one followingetching process.

In a third example, an average of a thickness 352 of the first sidewalllayer 350 may be between about 1 nanometer (nm) and about 5 nm.

In a fourth example, a distance 362 between a first portion (a portionnext to the spacer 334) of the first metal gate 330 and a second portion(a portion next to the spacer 344) of the first sidewall layer 350 maybe between about 15 nm and 45 nm.

In a fifth example, a width 335 of the first metal gate 330 is betweenabout 10 nm and about 30 nm, and a width 345 of the second metal gate340 is between about 10 nm and about 30 nm.

In FIG. 3, a first chemical mechanical polishing (CMP) process may beoptionally performed to planarize the first metal gate 330, the secondmetal gate 340, and the first sidewall layer 350.

In FIG. 4, the oxidation layer 360 and part of the first sidewall layer350 underlying the oxidation layer 360 are etched to expose the siliconsubstrate 320 underlying the oxidation layer 360. A contact profile 410is thus defined between the first metal gate 330 and the second metalgate 340 in an interposed manner. Part of the first sidewall layer 350that is in direct contact with the first metal gate 330 and the secondmetal gate 340 may also be slightly etched.

In one example, the oxidation layer 360 and part of the first sidewalllayer 350 underlying the oxidation layer 360 may be etched using anisotropic etching process. In another example, the isotropic etchingprocess is an ion bombardment process.

In FIG. 5, a silicide portion 520 is deposited following the contactprofile 410 in an exposed portion of the silicon substrate 320.

In one example, the silicide portion 520 is deposited using a materialselected from the group consisting of Ti_((1-x))Si_(x),Co_((1-x))Si_(x), Ni_((1-x))Si_(x), Ti_((1-x))Si_(x)Ge,Co_((1-x))Si_(x)Ge, and Ni_((1-x))Si_(x)Ge.

In FIG. 6, a second sidewall layer 630 is substantially formed to coverthe first sidewall layer 350 and to at least partially cover thesilicide portion 520.

In a first example, the second sidewall layer 630 is formed using amaterial selected from the group consisting of SiO_(x),SiO_(x)C_((1-x)), SiN_(x), SiO_((1-x))N_(x), SiC_((1-x))N_(x),SiO_((1-x-y))C_(x)N_(y), Ti_((1-x))N_(x), and Al_((1-x))N_(x).

In a second example, an average of a thickness 640 of the secondsidewall layer 630 is between about 10 angstrom (Å) and about 50 Å.

In FIG. 7, a metal glue layer 740 is deposited around the first metalgate 330 and the second metal gate 340. A trench 750 is thus definedabove the silicide portion 520 by the metal glue layer 750. A metal plug760 is then deposited within the trench 750.

In one example, the metal glue layer 740 is deposited using tungsten. Inanother example, the metal plug 760 is deposited using tungsten.

In FIG. 7, because of a tapered structure of the trench 750 formed withthe aid of the first sidewall layer 350 and the second sidewall layer630, an aspect ratio of the trench 750 may be reduced.

In FIG. 8, a second CMP process is performed on the metal plug 760, themetal glue layer 740, the first metal gate 330, the second metal gate340, the first sidewall layer 350, and the second sidewall layer 630 forplanarizing the metal plug 760, the metal glue layer 740, the firstmetal gate 330, the second metal gate 340, the first sidewall layer 350,and the second sidewall layer 630.

In the first embodiment, the first sidewall layer 350 and the secondsidewall layer 630 are used for separating the first metal gate 330 orthe second metal gate 340 from the metal plug 760 for reducing hole andelectron scattering. In FIG. 8 since the aspect ratio of the trench 750is reduced, a contact area of a bottom of the metal plug 760 will bemore accessible in comparison to the contact area at the bottom of thecontact layer 210. Therefore, resistance of the contact area of themetal plug 760 may be easier to control, and fitting a size of thecontact area of the metal plug 760 to better critical dimensionuniformity (CDU) may be easier.

In the first embodiment, because a hard mask layer is not used, defectscaused by using a hard mask layer are reduced.

In the first embodiment, since the high-K metal gate last process isperformed in advance, the silicide portion 520 suffers only minimaldamage by the high temperature of the high-K metal gate last process.

In a second embodiment, the first sidewall layer is thick enough toseparate the first metal gate or the second metal gate from the metalplug for reducing hole and electron scattering, so that the secondsidewall layer need not be used.

FIGS. 9-10 illustrate various cross-sectional views of a contactstructure 900 of a gate structure during formation of the contactstructure according to the second embodiment.

Before the formation of the contact structure 900 shown in FIG. 9, theprocesses shown in FIGS. 3-5 are performed.

In FIG. 9, the contact structure 900 includes a silicon substrate 960, afirst metal gate 910, a second metal gate 920, a first sidewall layer930, and a silicide layer 950.

The first metal gate 910 includes a first metal body 912 and a firstspacer 914 for at least partially coating the first metal body 912. Thesecond gate 920 includes a second metal body 922 and a second spacer 924for at least partially coating the second metal body 922.

A metal glue layer 940 is deposited around the first metal gate 910 andthe second metal gate 920. A trench 970 is thus defined above thesilicide portion 950 by the metal glue layer 940. A metal plug 980 isthen deposited within the trench 970.

Similarly, because of a tapered structure of the trench 970 formed withthe aid of the first sidewall layer 930, an aspect ratio of the trench970 may be reduced.

In FIG. 10, a CMP process is performed on the metal plug 980, the metalglue layer 940, the first metal gate 910, the second metal gate 920, andthe first sidewall layer 930 for planarizing metal plug 980, the metalglue layer 940, the first metal gate 910, the second metal gate 920, andthe first sidewall layer 930.

In the second embodiment, since the aspect ratio of the trench 970 isreduced, the abovementioned advantages of the contact structure 300 mayalso be taken by the contact structure 900. Repeated descriptions aboutadvantages of the contact structure 900 are saved for brevity.

FIG. 11 illustrates a flowchart of a method of forming a contactstructure of a contact structure according to the first embodiment.

In FIG. 11, the method includes the following stages: Optionally performa first CMP process on a first metal gate, a second metal gate, and afirst sidewall layer (1102). Etch an oxidation layer and the firstsidewall layer disposed between the first metal gate and the secondmetal gate to expose an underlying silicon substrate (1104). Deposit asilicide portion defined by a contact profile in the exposed portion ofthe silicon substrate (1106). Form a second sidewall layer substantiallycovering the first sidewall layer and at least partially covering thesilicide portion (1108). Deposit a metal glue layer around the firstmetal gate and the second metal gate defining a trench above thesilicide portion (1110). Deposit a metal plug within the trench (1112).Performing a second CMP process on the metal plug, the metal glue layer,the first metal gate, the second metal gate, the first sidewall layer,and the second sidewall layer (1114).

FIG. 12 illustrates a flowchart of a method of forming a contactstructure of a contact structure according to the second embodiment.

In FIG. 12, the method includes the following stages: Optionally performa first CMP process on a first metal gate, a second metal gate, and afirst sidewall layer (1202). Etch an oxidation layer and the firstsidewall layer disposed between the first metal gate and the secondmetal gate to expose an underlying silicon substrate (1204). Deposit asilicide portion defined by a contact profile in the exposed portion ofthe silicon substrate (1206). Deposit a metal glue layer around thefirst metal gate and the second metal gate defining a trench above thesilicide portion (1208). Deposit a metal plug within the trench (1210).Perform a second CMP process on the metal plug, the metal glue layer,the first metal gate, the second metal gate, and the first sidewalllayer (1212).

This disclosure teaches a method of forming a contact structure of agate structure. In this method, an oxidation layer and a first sidewalllayer disposed between a first metal gate and a second metal gate areetched to expose an underlying silicon substrate. A silicide portiondefined by a contact profile in the exposed portion of the siliconsubstrate is deposited. A second sidewall layer substantially coveringthe first sidewall layer and at least partially covering the silicideportion is formed after the silicide portion is deposited. A metal gluelayer is deposited around the first metal gate and the second metal gatedefining a trench above the silicide portion. A metal plug is depositedwithin the trench.

This disclosure also teaches a method of forming a contact structure ofa gate structure. In the method, an oxidation layer and a first sidewalllayer disposed between a first metal gate and a second metal gate areetched to expose an underlying silicon substrate. A silicide portiondefined by a contact profile is deposited in the exposed portion of thesilicon substrate. A metal glue layer is deposited around the firstmetal gate and the second metal gate defining a trench above thesilicide portion. A metal plug is deposited within the trench.

This disclosure also teaches a contact structure of a gate structure.The contact structure includes a silicide portion, a first metal gate, asecond metal gate, a first sidewall layer, a metal glue layer, and ametal plug. The silicide portion is formed in the silicon substrate. Thefirst metal gate is formed above the silicon substrate. A second metalgate is formed above the silicon substrate. A first sidewall layer atleast partially covers a first lateral side of the first metal gate anda second lateral side of the second metal gate. The first sidewall layeris interposed between the first metal gate and the second metal gate.The first lateral side of the first metal gate is oppose to the secondlateral side of the second metal gate. A metal glue layer is depositedaround the first metal gate and the second metal gate defining a trenchabove the silicide portion. A metal plug is deposited within the trench.

This written description uses examples to disclose embodiments of thedisclosure, include the best mode, and also to enable a person ofordinary skill in the art to make and use various embodiments of thedisclosure. The patentable scope of the disclosure may include otherexamples that occur to those of ordinary skill in the art. One ofordinary skill in the relevant art will recognize that the variousembodiments may be practiced without one or more of the specificdetails, or with other replacement and/or additional methods, materials,or components. Well-known structures, materials, or operations may notbe shown or described in detail to avoid obscuring aspects of variousembodiments of the disclosure. Various embodiments shown in the figuresare illustrative example representations and are not necessarily drawnto scale. Particular features, structures, materials, or characteristicsmay be combined in any suitable manner in one or more embodiments.Various additional layers and/or structures may be included and/ordescribed features may be omitted in other embodiments. Variousoperations may be described as multiple discrete operations in turn, ina manner that is most helpful in understanding the disclosure. However,the order of description should not be construed as to imply that theseoperations are necessarily order dependent. In particular, theseoperations need not be performed in the order of presentation.Operations described herein may be performed in a different order, inseries or in parallel, than the described embodiments. Variousadditional operations may be performed and/or described. Operations maybe omitted in additional embodiments.

This written description and the following claims may include terms,such as left, right, top, bottom, over, under, upper, lower, first,second, etc. that are used for descriptive purposes only and are not tobe construed as limiting. For example, terms designating relativevertical position may refer to a situation where a device side (oractive surface) of a substrate or integrated circuit is the “top”surface of that substrate; the substrate may actually be in anyorientation so that a “top” side of a substrate may be lower than the“bottom” side in a standard terrestrial frame of reference and may stillfall within the meaning of the term “top.” The term “on” as used herein(including in the claims) may not indicate that a first layer “on” asecond layer is directly on and in immediate contact with the secondlayer unless such is specifically stated; there may be a third layer orother structure between the first layer and the second layer on thefirst layer. As an example, the structures, layouts, materials,operations, voltage levels, or current levels related to “source” and“drain” described herein (including in the claims) may beinterchangeable as a result of transistors with “source” and “drain”being symmetrical devices. The term “substrate” may refer to anyconstruction comprising one or more semiconductive materials, including,but not limited to, bulk semiconductive materials such as asemiconductive wafer (either alone or in assemblies comprising othermaterials thereon), and semiconductive material layers (either alone orin assemblies comprising other materials). The embodiments of a deviceor article described herein can be manufactured, used, or shipped in anumber of positions and orientations. Persons skilled in the art willrecognize various equivalent combinations and substitutions for variouscomponents shown in the figures.

What is claimed is:
 1. A method of forming a contact structure of a gatestructure, comprising: etching an oxidation layer and a first sidewalllayer disposed between a first metal gate and a second metal gate toexpose an underlying silicon substrate; depositing a silicide portiondefined by a contact profile in the exposed portion of the siliconsubstrate; forming a second sidewall layer substantially covering thefirst sidewall layer and at least partially covering the silicideportion after the depositing the silicide portion; depositing a metalglue layer around the first metal gate and the second metal gatedefining a trench above the silicide portion; and depositing a metalplug within the trench.
 2. The method of claim 1, further comprising:performing a first chemical-mechanical polishing (CMP) process on thefirst metal gate, the second metal gate, the first sidewall layer, andthe oxidation layer before the etching the oxidation layer and the firstsidewall.
 3. The method of claim 1, further comprising: performing asecond CMP process on the metal plug, the metal glue layer, the firstmetal gate, the second metal gate, the first sidewall layer, and thesecond sidewall layer.
 4. The method of claim 1, wherein the etching theoxidation layer and the first sidewall layer to expose the underlyingsilicon substrate comprises performing an isotropic etching processsubstantially on the oxidation layer and the first sidewall layer. 5.The method of claim 4, wherein the isotropic etching process is an ionbombardment process.
 6. The method of claim 1, further comprising:forming the first sidewall layer using a material selected from thegroup consisting of SiN_(x), SiO_((1-x))N_(x), SiC_((1-x))N_(x),SiO_((1-x-y))C_(x)N_(y), Ti_((1-x))N_(x), and Al_((1-x))N_(x); whereinthe forming the second sidewall layer comprises forming the secondsidewall layer using a material selected from the group consisting ofSiO_(x), SiO_(x)C_((1-x)), SiN_(x), SiO_((1-x))N_(x), SiC_((1-x))N_(x),SiO_((1-x-y))C_(x)N_(y), Ti_((1-x))N_(x), and Al_((1-x))N_(x); andwherein the depositing the silicide portion comprises depositing thesilicide portion using a material selected from the group consisting ofTi_((1-x))Si_(x), Co_((1-x))Si_(x), Ni_((1-x))Si_(x),Ti_((1-x))Si_(x)Ge, Co_((1-x))Si_(x)Ge, and Ni_((1-x))Si_(x)Ge.
 7. Amethod of forming a contact structure of a gate structure, comprising:etching an oxidation layer and a first sidewall layer disposed between afirst metal gate and a second metal gate to expose an underlying siliconsubstrate; depositing a silicide portion defined by a contact profile inthe exposed portion of the silicon substrate; depositing a metal gluelayer around the first metal gate and the second metal gate defining atrench above the silicide portion; and depositing a metal plug withinthe trench.
 8. The method of claim 7, further comprising: performing afirst chemical mechanical polishing (CMP) process on the first metalgate, the second metal gate, the first sidewall layer, and the oxidationlayer before the etching the oxidation layer and the first sidewall. 9.The method of claim 7, further comprising: performing a second CMPprocess on the metal plug, the metal glue layer, the first metal gate,the second metal gate, and the first sidewall layer.
 10. The method ofclaim 7, further comprising: forming a second sidewall layersubstantially covering the first sidewall layer and at least partiallycovering the silicide portion after the depositing the silicide portion.11. The method of claim 10, wherein forming the second sidewall layerfurther comprises forming the second sidewall layer by using a materialselected from the group consisting of SiO_(x), SiO_(x)C_((1-x)),SiN_(x), SiO_((1-x))N_(x), SiC_((1-x))N_(x), SiO_((1-x-y))C_(x)N_(y),Ti_((1-x))N_(x), and Al_((1-x))N_(x).
 12. The method of claim 10,wherein forming the second sidewall layer further comprises forming thesecond sidewall layer with an average thickness between about 10angstrom (Å) and about 50 Å.
 13. The method of claim 7, furthercomprising forming the first sidewall layer by using a nitride-basedfilm.
 14. The method of claim 13, further comprising forming the firstsidewall layer by using a material selected from the group consisting ofSiN_(x), SiO_((1-x))N_(x), SiC_((1-x))N_(x), SiO_((1-x-y))C_(x)N_(y),Ti_((1-x))N_(x), and Al_((1-x))N_(x).
 15. The method of claim 13,wherein forming the first sidewall layer further comprises forming thefirst sidewall layer with an average thickness between about 1 nanometer(nm) and about 5 nm.
 16. A method of forming a contact structure of agate structure, comprising: etching an oxidation layer and a firstsidewall layer disposed between a first metal gate and a second metalgate to expose an underlying silicon substrate; depositing a silicideportion defined by a contact profile in the exposed portion of thesilicon substrate; depositing a metal glue layer around the first metalgate and the second metal gate defining a trench above the silicideportion; depositing a metal plug within the trench; and performing afirst chemical mechanical polishing (CMP) process on the first metalgate, the second metal gate, the first sidewall layer, and the oxidationlayer before the etching the oxidation layer and the first sidewall. 17.The method of claim 16, further comprising: performing a second CMPprocess on the metal plug, the metal glue layer, the first metal gate,the second metal gate, and the first sidewall layer.
 18. The method ofclaim 16, further comprising: forming a second sidewall layersubstantially covering the first sidewall layer and at least partiallycovering the silicide portion after the depositing the silicide portion.19. The method of claim 18, wherein forming the second sidewall layerfurther comprises forming the second sidewall layer by using a materialselected from the group consisting of SiO_(x), SiO_(x)C_((1-x)),SiN_(x), SiO_((1-x))N_(x), SiC_((1-x))N_(x), SiO_((1-x-y))C_(x)N_(y),Ti_((1-x))N_(x), and Al_((1-x))N_(x).
 20. The method of claim 18,wherein forming the second sidewall layer further comprises forming thesecond sidewall layer with an average thickness between about 10angstrom (Å) and about 50 Å.